The present invention relates generally to the reliability of a replaceable element in a complex system. The invention relates more importantly to the life remaining for a replaceable element so that timely replacement may be made without unduly increasing operation costs resulting from too early a replacement or in the alternative a parts failure from waiting too long to replace. The invention relates in particular with regards high frequency service items (HFSI) and customer replaceable units (CRU). The invention relates more particularly to using counters to determine replacement of HFSI and CRU in document processing systems.
Current day machine architecture allows for the use of HFSI counters, which keep track of the number of copies/prints that utilize certain key components in a document processing system and, thus, contribute to their wear. There are a number of these counters typically each associated with a particular replaceable element so that they can be reset independently when, for example, a photoreceptor is replaced. Many replaceable parts have such a counter associated with them. They are useful in a service strategy where the individual part is scheduled for replacement when the counter associated with that part reaches a predetermined value (the xe2x80x9clifexe2x80x9d of the part). The idea is to replace parts just before they fail so as to avoid unnecessary machine down time and loss of productivity. When the part is replaced, the associated HFSI counter is reset to zero. These predetermined values are obtained by examination of a population of the parts in question, determining the mean time between failure, and a judgment on the expected life of the part is made. This judgment targets the replacement of the part just before the average life of the part as measured in xe2x80x9cclicksxe2x80x9d has transpired. By xe2x80x9cclicksxe2x80x9d what is meant is the number of iterations of system cyclesxe2x80x94usually the number of prints/copies made in a document processing system for example. The problem here is that this judgment needs to provide a conservative estimate of life so that the part does not fail before the scheduled replacement date which means that a certain measure of useful life is being wasted.
The counters are also implemented in a way that the specific counts are only incremented when the pertinent features are being utilized. So in a copier or printer for example, any counters associated with Tray 2 are not incremented when only Tray 1 is being used. Each part so designated has its own counter.
In U.S. Pat. No. 4,496,237 to Schron, the invention described discloses a reproduction machine having a non-volatile memory for storing indications of machine consumable usage such as photoreceptor, exposure lamp and developer, and an alphanumeric display for displaying indications of such usage. In operation, a menu of categories of machine components is first scrolled on the alphanumeric display. Scrolling is provided by repetitive actuation of a scrolling switch. Having selected a desired category of components to be monitored by appropriate keyboard entry, the sub-components of the selected category can be scrolled on the display. In this manner, the status of various consumables can be monitored and appropriate instructions displayed for replacement. In another feature, the same information on the alphanumeric display can be remotely transmitted. The above is herein incorporated by reference in its entirety for its teaching.
The difficulty with the current scenario is that xe2x80x9cclicksxe2x80x9d alone are not an accurate measure of the wear experienced by system components. The use of a simple, non-specific, incremental value to track the wear on all components does not acknowledge the specific stresses that each individual component faces and, thus, is inaccurate in assessing the remaining life available for the part. One xe2x80x9cclickxe2x80x9d will correspond to different wear increments for different parts. There are many situations where a part is exercised much more than the click count would indicate and some where it is exercised less. In particular, during system recovery there is an often an overhead to clearing, cleaning and resetting the system. For example, in document processing systems when a paper jam occurs considerable extra wear may be incurred in recovering from the jam in the clearing of the paper path and the cleaning of the image path. When the HFSI counter is grossly inaccurate on the low side, parts are considered OK when in fact their useful life has expired. The part fails and the device becomes inoperable and unproductive until the customer service engineer arrives, identifies the failure, and repairs the machine. If the estimate is too high, the part is replaced even though it has a measure of useful life remaining. Either case leads to inefficiencies in the parts replacement strategy and incurs increased costs thereby.
Therefore, as discussed above, there exists a need for an arrangement and methodology which will solve the problem of preventing machine system down time without unnecessarily incurring costs from too early or too late a replacement. Thus, it would be desirable to solve this and other deficiencies and disadvantages as discussed above with an improved methodology for more accurately accounting and monitoring wear characteristics in complex systems.
The present invention relates to a method for assessing an end of life determination for a replaceable element in a system comprising accepting a system cycle as a nominal count while monitoring the system for a recovery condition and providing a recovery count in the event of the recovery condition. This is followed by summing the nominal count and the recovery count into a supplemental diagnostic counter.
In particular, the present invention relates to a method for assessing end of life determinations for high frequency service items in a document processing system comprising accepting a document processing system cycle as a nominal count and applying at least one weighting factor to the nominal count to yield at least one weighted count while monitoring the system for a recovery condition. This is followed by providing a recovery count in the event of the recovery condition and summing the one or more weighted counts and the recovery count into a supplemental diagnostic counter.
The present invention also relates to a method of assessing end of life determinations for a high frequency service item in a document processing system comprising incrementing a nominal counter by a nominal count for each cycle of the document processing system and applying at least one weighting factor to the nominal count to yield a weighted count. The method further comprises monitoring the system for a recovery condition, providing a recovery count in the event of the recovery condition, and monitoring the system for a startup condition also providing a startup count in the event of the startup condition. The method then comprises monitoring the system for a cycle-down condition, providing a cycle-down count in the event of the cycle-down condition and summing the nominal count, the weighted count, the recovery count, the startup count and the cycle-down count into a supplemental diagnostic counter.